This invention relates to a high-speed cast process and apparatus for making an improved film or sheet product with integral fastening elements. More particularly, this invention relates to a method and apparatus for in-line fusing of closure profiles, including any base portions, with a layer of film or sheet, the film or sheet with the closure profiles being converted into containers such as bags.
One such process is that described in U.S. Pat. No. 4,263,079 ('079) issued Apr. 21, 1981, and assigned to the same assignee as is the present invention. In that invention the fastener elements are extruded separately and joined to the mainstream film body or sheet very closely to the location where the film or sheet exits from the die lips so that the joining occurs before significant cooling of the extrudate.
The process taught by the '079 reference results in the introduction of lateral stress in the mainstream film body. Those skilled in the art will appreciate that this lateral stress results from the longitudinal stretching and concurrent restriction of the lateral edges of the mainstream film body. The process taught by the '079 reference results in thinning of the mainstream film body immediately adjacent to the separately extruded fastening elements. This thinning is a manifestation of the lateral stress present in the mainstream film body.
Attempts to compensate for this thinning by tapering the edges of the base of the closure profiles have proven unsatisfactory. This is because the tapered edges tend to curl up rather than adhere to the mainstream film layer.